Method of manufacturing suspension structure and chamber

ABSTRACT

A method of manufacturing a suspension structure including providing a substrate, forming a hole and a sacrificial layer filling the hole on the substrate, forming a patterned photoresist layer on the substrate and the sacrificial layer, the patterned photoresist layer exposing a part of the substrate and the sacrificial layer, forming a structure layer on the substrate, the patterned photoresist layer, and the sacrificial layer, performing a lift off process to remove the patterned photoresist layer and the structure layer above the photoresist pattern, and performing a dry etch process to remove the sacrificial layer in order to make the structure layer and the hole become the suspension structure and the chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a suspensionstructure and chamber, and more particularly, to a method ofmanufacturing a suspension structure and chamber using a sacrificiallayer, dry etching process, and lift off process.

2. Description of the Prior Art

Micro-electromechanical systems (MEMS) are modern technology, whichcoordinate electrical circuits and mechanics. MEMS have been applied tofabricate devices with both electrical circuits and mechanical elements,such as pressure sensors, accelerators, and micro-microphones. Thesuspended structure is applied in many MEMS devices such as a MEMSswitch, an inkjet nozzle, and micro-microphones, etc., but the method ofmanufacturing a suspension structure according to the prior art stillhas many limitations.

Please refer to FIG. 1 to FIG. 4. FIG. 1 to FIG. 4 shows the method ofmanufacturing a suspension structure and chamber by using wet etchingprocess according to the prior art. As shown in FIG. 1, a metaldeposition process is performed on a semiconductor substrate 12 to forman adhesive layer. Before a copper (Cu) metal layer is deposited as astructure layer, the metal deposition process deposits a titanium (Ti)metal layer 14 as an adhesive layer between the semiconductor substrate12 and the Cu metal layer 16, and the Ti metal layer 14 is deposited onthe semiconductor substrate 12 by using an electron gun evaporationsystem in the metal deposition process. Next, the Cu metal layer 16 isdeposited on the Ti metal layer 14, and there are two methods forperforming the metal deposition process of the Cu metal layer 16. Thefirst method is directly using the electron gun evaporation system todeposit the Cu metal layer 16 with thickness of about 1 micrometer. Thesecond method is using the electron gun evaporation system to deposit aseed layer first, and then deposit the Cu metal layer 16 on the seedlayer by electroplating process. Next, a passivation layer 18 isdeposited to protect the Cu metal layer 16. For example, a metal layerof nickel (Ni), chromium (Cr), Ti, or aurum (Au) is deposited as thepassivation layer 18 by using the electron gun evaporation system. Then,a photoresist layer 20 is coated on the passivation layer 18 by using aspin coating machine.

As shown in FIG. 2, a first photoresist pattern 22 is formed by aphotolithography process on the photoresist layer 20, and then a portionof the passivation layer 18, the Cu metal layer 16, and the Ti metallayer 14 that are not protected by the first photoresist pattern 22 areremoved in sequence by a etching process. Next, the first photoresistpattern 22 is removed, and a second photoresist pattern 24 is formed onthe passivation layer 18 and the semiconductor substrate 12, as shown inFIG. 3.

At last, a wet etching process using the KOH etching liquid, forexample, is performed to form a chamber 26 on the semiconductorsubstrate 12 to form the suspension structure 10, and the secondphotoresist pattern 24 is removed, as shown in FIG. 4.

The method of manufacturing a suspension structure according to theprior art has some disadvantages as follows. First, the KOH etchingliquid can etch aluminum (Al), and few materials can serve as an etchingmask for the KOH etching liquid, only LPCVD Si3N4 or low stress Si3N4for example. Therefore, the prior art has to use specific metal that isnot able to be etched by the KOH etching liquid, or form extrapassivation layers and adhesive layers above and under the structurelayer respectively. Second, since the prior art uses the wet etchingprocess to remove the semiconductor substrate to form a chamber in thesemiconductor substrate, the suspension structure will be affected bythe surface tension of the etching liquid, which results in a brokenstructure layer or the suspension part sticking to the substratesurface. Third, it is very difficult for the prior art methods to designand manufacture the suspension structure and chamber with various shapesby adjusting the process parameters.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method ofmanufacturing a suspension structure and chamber to solve thedisadvantages and problems of the prior art, and improve the processyield and reduce the cost.

According to the claims, the present invention provides a method ofmanufacturing a suspension structure and chamber comprising providing asubstrate, forming a first photoresist pattern on the substrate, heatingthe first photoresist pattern to harden it as a sacrificial layer,forming a second photoresist pattern on the substrate and thesacrificial layer, the second photoresist pattern exposing a part of thesubstrate and the sacrificial layer, forming a structure layer on thesubstrate, the second photoresist pattern, and the sacrificial layer,performing a lift off process to remove the second photoresist patternand the structure layer above the second photoresist pattern, andperforming a dry etching process to remove the sacrificial layer inorder to make the structure layer on the substrate and the sacrificiallayer become the suspension structure and the hole on the substratebecome the chamber.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 to FIG. 4 shows the method of manufacturing a suspensionstructure and chamber by using wet etching process according to theprior art.

FIG. 5 to FIG. 9 shows the method of manufacturing a suspensionstructure and chamber in accordance with the first preferred embodimentof the present invention.

FIG. 10 to FIG. 14 shows the method of manufacturing a suspensionstructure and chamber in accordance with the second preferred embodimentof the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 5 to FIG. 9. FIG. 5 to FIG. 9 shows the method ofmanufacturing a suspension structure and chamber in accordance with thefirst preferred embodiment of the present invention. As shown in FIG. 5,a hole 103 is formed on the substrate 102 first, and a first patternedphotoresist layer 104 is formed on the substrate 102, wherein thesubstrate 102 can be a silicon wafer or a SOI, but is not limited tothis. The method of forming the hole 103 can include a wet etchingprocess, a sputtering etching process, a plasma etching process, or areactive ion etching (RIE) process, and the shape of the hole 103 can bea semicircle, semi-ellipse, trapezoid, rectangle, trapezoid with roundcorners, or rectangle with round corners by adjusting the processparameters to meet the requirement of different MEMS devices.

Next, as shown in FIG. 6, since the photoresist will be fluid and thenhardened after being heated, the first patterned photoresist layer 104is heated to be hardened as a sacrificial layer 106. The process ofheating the first patterned photoresist layer 104 can be performed usingan oven or heating plate, etc. In the first preferred embodiment of thepresent invention, the sacrificial layer 106 has tilted sidewalls byadjusting the heating process parameters such as the heating temperatureand time, as shown in FIG. 6.

Next, as shown in FIG. 7, a second patterned photoresist layer 108 isformed on the substrate 102 and the sacrificial layer 106, and thesecond patterned photoresist layer 108 exposes a part of the substrate102 and the sacrificial layer 106, and then a structure layer 110 isformed on the substrate 102, the second patterned photoresist layer 108,and the sacrificial layer 106. The structure layer 110 can includemonocrystalline silicon, polycrystalline silicon, amorphous silicon, ormetals such as Al or Cu, etc., and the method of forming the structurelayer 110 can include a chemical vapor deposition (CVD) process or aplating process. In addition, if the CVD process is chosen to form thestructure layer 110, an atmospheric pressure chemical vapor deposition(APCVD) process can be used in the present invention to make thestructure layer 110 smoother on the surface.

Next, as shown in FIG. 8, a lift off process is performed, and thesecond patterned photoresist layer 108 and the structure layer 110 abovethe second patterned photoresist layer 108 are removed by a wet etchingprocess. At last, as shown in FIG. 9, a dry etching process is performedto remove the sacrificial layer 106 in order to make the structure layer110 above the substrate 102 and the sacrificial layer 106 become thesuspension structure 100 and the chamber 120, wherein the dry etchingprocess can include a sputtering etching process, a plasma etchingprocess, or a RIE process.

Please refer to FIG. 10 to FIG. 14. FIG. 10 to FIG. 14 shows the methodof manufacturing a suspension structure and chamber in accordance withthe second preferred embodiment of the present invention. As shown inFIG. 10, a hole 203 is formed on the substrate 202 first, and a firstpatterned photoresist layer 204 is formed on the substrate 202, whereinthe substrate 202 can be a silicon wafer or a SOI, but is not limited tothis. The method of forming the hole 203 can include a wet etchingprocess, a sputtering etching process, a plasma etching process, or aRIE process, and the shape of the hole 203 can be a semicircle,semi-ellipse, trapezoid, rectangle, trapezoid with round corners, orrectangle with round corners by adjusting the process parameters to meetthe requirement of different MEMS devices.

Next, as shown in FIG. 11, since the photoresist will be fluid andhardened after being heated, the first patterned photoresist layer 204is heated to be hardened as a sacrificial layer 206. The process ofheating the first patterned photoresist layer 204 can be performed usingan oven or heating plate, etc. In the second preferred embodiment of thepresent invention, the sacrificial layer 206 has tilted sidewalls withround corners by adjusting the heating process parameters such as theheating temperature and time, as shown in FIG. 11.

Next, as shown in FIG. 12, a second patterned photoresist layer 208 isformed on the substrate 202 and the sacrificial layer 206, and thesecond patterned photoresist layer 208 exposes a part of the substrate202 and the sacrificial layer 206, and then a structure layer 210 isformed on the substrate 202, the second patterned photoresist layer 208,and the sacrificial layer 206, wherein the structure layer 210 caninclude metals, monocrystalline silicon, polycrystalline silicon, oramorphous silicon, and the method of forming the structure layer 210 caninclude a CVD process or a plating process.

Next, as shown in FIG. 13, a lift off process is performed, and thesecond patterned photoresist layer 208 and the structure layer 210 abovethe second patterned photoresist layer 208 are removed by a wet etchingprocess. At last, as shown in FIG. 14, a dry etching process isperformed to remove the sacrificial layer 206 in order to make thestructure layer 210 above the substrate 202 and the sacrificial layer206 become the suspension structure 200 and the chamber 220, wherein thedry etching process can include a sputtering etching process, a plasmaetching process, or a RIE process.

Since the method of the present invention utilizes the photoresist asthe sacrificial layer to form the suspension structure, thereforemonocrystalline silicon, polycrystalline silicon, amorphous silicon, ormetals such as Al or Cu, etc. can be used for the structure layer, andthe structure layer is not limited to using a specific metal that is notable to be etched by the KOH etching liquid. In addition, the method ofthe present invention utilizes the dry etching process to remove thesacrificial layer, and therefore the suspension structure will not beaffected by the surface tension of the etching liquid, which results inthe broken structure layer or the suspension part sticking to thesubstrate surface. Furthermore, please note that the present inventionutilizes the photoresist after being heated and hardened as thesacrificial layer so that the suspension structure will not be brokeneasily due to bad covering at the corners, and the present invention candesign and manufacture the suspension structure and the chamber withvarious shapes by controlling shape of the photoresist after beingheated and hardened to substantially increase the application fields ofthe suspension structure.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A method of manufacturing a suspension structure comprising:providing a substrate; forming a hole on the substrate; forming a firstpatterned photoresist layer on the substrate and the first patternedphotoresist layer filling the hole; heating the patterned photoresistlayer to harden it as a sacrificial layer; forming a second patternedphotoresist layer on the substrate and the sacrificial layer, the secondpatterned photoresist layer exposing a part of the substrate and thesacrificial layer; forming a structure layer on the substrate, thesecond patterned photoresist layer, and the sacrificial layer;performing a lift off process to remove the second patterned photoresistlayer and the structure layer above the second patterned photoresistlayer; and performing a dry etching process to remove the sacrificiallayer in order to make the structure layer on the substrate and thesacrificial layer become the suspension structure and the hole on thesubstrate become the chamber.
 2. The method of claim 1, wherein thesacrificial layer has sidewalls with round corners.
 3. The method ofclaim 1, wherein the sacrificial layer has tilted sidewalls.
 4. Themethod of claim 1, wherein the structure layer comprises metal.
 5. Themethod of claim 1, wherein the structure layer comprises monocrystallinesilicon, polycrystalline silicon, or amorphous silicon.
 6. The method ofclaim 1, wherein the method of forming the structure layer comprises achemical vapor deposition process of a plating process.
 7. The method ofclaim 1, wherein the chemical vapor deposition (CVD) process comprisesan atmospheric pressure chemical vapor deposition process.
 8. The methodof claim 1, wherein the lift off process comprises a wet etchingprocess.
 9. The method of claim 1, wherein the dry etching processcomprises a sputtering etching process, a plasma etching process, or areactive ion etching (RIE) process.